Session 5 - Parotid Gland and Submandibular Triangle - LabLink
Note: The donor’s head and neck have been mid-sagittally sectioned by the Anatomy faculty and DAS staff. Sectioning of the head will facilitate your efforts in dissecting for the rest of the course. If you have any questions about this process, please discuss with faculty.
Click here for a condensed, step-by-step dissection summary.
Locate and identify the relevant osteological features
Find these structures:
- Temporal bone
- External acoustic meatus
- Mastoid notch
- Mastoid process
- Styloid process
- Mandibular fossa
- Petrotympanic fissure
- Zygomatic process
- Stylomastoid foramen
- Tympanic canaliculus
- Groove for greater petrosal n.
- Groove for lesser petrosal n.
- Condylar process
- Cranial base
- Jugular foramen
Skin superficial to the parotid gland, and remove parotid fascia
Find these structures:
- Parotid gland
- Accessory parotid gland
- Parotid (Stensen’s) duct
- Papilla of parotid duct
1.) Begin removing skin from a point medial to the ear. Locate the entirety of the parotid gland, and remove all skin superficial to the gland without damaging any structures exiting the gland, particularly the facial n. (CN VII) branches. Do NOT skin the rest of the face.
Photo 1. Procedural: face, lateral
Note: The parotid gland is found at the inferolateral aspect of the face. The gland is located in the parotid fossa, an irregular space bordered by the ramus of the mandible and masseter m. anteriorly, the mastoid process and sternocleidomastoid m. posteriorly, the temporomandibular joint (TMJ) and external acoustic meatus superiorly, and the angular tract (a thick band of connective tissue, extending from the angle of the mandible to the hyoid bone) inferiorly.
Note: Parotid fascia invests the parotid gland. The parotid gland contains branches of the facial n. (CN VII), which innervate facial mm.
Note: The parotid gland is innervated by preganglionic parasympathetic fibers originating in the glossopharyngeal n. (glossopharyngeal n. → tympanic n. → lesser petrosal n.). These fibers synapse in the otic ganglion, which is associated in location with the deep portion of the mandibular n. (V3) trunk, just inferior to the foramen ovale. Postganglionic fibers are transmitted to the parotid gland via the auriculotemporal n. (of V3).
2.) Locate the proximal portion of the parotid (Stensen’s) duct as it exits the parotid gland. Small branches of the facial n. (CN VII) will likely also be visible in this area. Do NOT dissect or follow the duct or facial n. branches at this time. Occasionally, a small accessory parotid gland is present.
Note: The parotid (Stensen’s) duct typically arises at the anterior border of the parotid gland, travels superficial to the masseter m., and dives deep to (and through) the buccinator m. The parotid duct is variable in path and size, but is typically 1-3 mm in diameter. The parotid duct conducts saliva from the parotid gland, through the buccinator m., opening through the papilla of parotid (Stensen’s) duct opposite the maxillary second molars.
Note: The facial n. exits the stylomastoid foramen, then divides into two divisions: the temporofacial division (superiorly) and the cervicofacial division (inferiorly). The temporofacial division typically gives rise to the temporal brs., zygomatic brs., and a portion of the buccal brs. The cervicofacial division typically gives rise to a portion of the buccal brs., marginal mandibular br., and the cervical br.
Note: The stylomastoid foramen is between the mastoid and styloid processes of the temporal bone, and transmits the facial n.
Note: Accessory parotid glands, if present, are typically located between the zygomatic arch superiorly and parotid duct inferiorly. These glands can be attached to the parotid gland proper, or more commonly detached.
Photo 2. Parotid gland with proximal portions of facial n. brs.
3.) Look into the the oral cavity of the donor. At approximately the level of the 2nd maxillary molars, locate the papilla of parotid gland of the oral mucosa.
Photo 3. Papilla of parotid duct
Locate neurovasculature superior to parotid gland and posterior to ear
Find these structures:
- Auriculotemporal n.
- Superficial temporal a. & v.
- Posterior auricular a. & v.
- Occipital a.
4.) Using blunt dissection superior to the parotid gland, locate the auriculotemporal n. and superficial temporal a. & v.
Note: The auriculotemporal n. is a branch of the mandibular n. (V3). The auriculotemporal n. serves three functions, germane to this lab:
- transmitting secretomotor postganglionic parasympathetic fibers to the parotid gland (from the otic ganglion; preganglionic fibers from glossopharyngeal n.),
- afferently serving the temporomandibular joint, and
- afferently serving the skin of the: tragus of the ear, the external auditory meatus, and the area anterosuperior to the ear.
Note: The cutaneous portion of the auriculotemporal n. may be found just posterior to, and accompanying, the superficial temporal a. and v. superiorly from the parotid gland.
Note: The superficial temporal a. and the maxillary a. are the terminal branches of external carotid a. The superficial temporal v. and the maxillary v. join to form the retromandibular v. The proximal portions of the superficial temporal a. & v. are located within the parotid gland.
Photo 4. Auriculotemporal n., cutaneous portion and superficial temporal a. & v.
5.) Locate the posterior auricular a. and occipital a. With removal of the trapezius in previous labs the occipital a. may have been removed.
Note: Posterior auricular a. can be located just posterior to the ear, and often anastomoses with the occipital a., which is more posteriorly located on the back of the scalp. The occipital a. is located with the greater occipital n., a branch of the dorsal primary ramus of spinal n. C2. Both the posterior auricular a. and occipital a. are branches of external carotid a.
Note: Posterior auricular a. supplies muscles in the anterior neck, including posterior belly of digastric m., sternocleidomastoid m., and stylohyoid m., as well as the parotid gland. The occipital a. supplies portions of the posterior scalp and neck, as well as lateral neck.
Photo 5. Origins of posterior auricular and occipital aa.
Unilaterally, complete a deep dissection of the parotid gland
Find these structures:
- Facial n. (CN VII)
- Retromandibular v.
- Superficial temporal v.
- Maxillary v.
- External jugular v.
- Posterior auricular v.
- Internal jugular v.
- Facial v.
6.) For the deep dissection, carefully remove portions of the parotid gland with blunt dissection. Trace facial n. branches to the temporofacial and cervicofacial divisions, and follow these divisions until they condense as a main trunk. Continue to trace the main trunk of the facial n. until you reach its emergence from the skull at the stylomastoid foramen. Alternatively, you could directly locate the stylomastoid foramen using targeted, blunt dissection, and then trace the main trunk of the facial n. toward the face.
Note: Three neurovascular structures typically travel through the the parotid gland (anterior to the external auditory meatus). From superficial-to-deep, they are the:
- facial n. (CN VII),
- retromandibular v., and
- external carotid a.
Photo 6. Facial n. emerging from the stylomastoid foramen
7.) Locate the retromandibular v., and follow it to the potential junctions with: 1) the facial v. (into the internal jugular v.), and 2) the posterior auricular v. (to form the external jugular v.).
Note: The superficial temporal v. typically unites with the maxillary v. to form the retromandibular v. The maxillary v. is a short vein formed by the coalescence of numerous veins of the pterygoid plexus. It accompanies the maxillary a.
Photo 7. Superficial temporal + maxillary v. = retromandibular v.
Note: The retromandibular v. may divide into anterior and posterior divisions. The anterior division of the retromandibular v. typically unites with the facial v. before joining with the internal jugular v. The posterior division of the retromandibular v. typically unites with the posterior auricular v. to form the external jugular v.
Photo 8. Retromandibular v.; anterior and posterior divisions
Clean and locate the muscles and submandibular gland in the deep neck
Find these structures:
- Digastric m.
- Anterior belly
- Posterior belly
- Stylohyoid m.
- Mylohyoid m.
- Hyoglossus m.
- Submandibular gland
- External carotid a.
- Superior thyroid a.
- Superior laryngeal a.
- Ascending pharyngeal a.
- Lingual a.
- Facial a.
- Superior thyroid a.
8.) Clean the anterior and posterior bellies of the digastric m.
Note: The digastric m. consists of two bellies (anterior and posterior) connected by an intermediate tendon. The anterior belly attaches to the mandible, the posterior belly attaches to the temporal bone, and the intermediate tendon anchors to the hyoid bone via a fibrous loop. Formed from the mesenchyme of the 1st (anterior) and 2nd (posterior) pharyngeal arches, each belly is separately innervated. The anterior belly is innervated by the nerve to mylohyoid (a branch of inferior alveolar n.,V3), whereas the posterior belly is innervated by the facial n. (CN VII). The digastric m. may either weakly depress the mandible, or elevate the hyoid bone.
Note: The submandibular (digastric) triangle is the most superior region of the anterior cervical triangle. It is bordered inferiorly by the anterior and posterior bellies of the digastric m., and superiorly by the mandible; typically contains the submandibular gland and the facial a. & v.
Photo 9. Submandibular triangle
9.) Within the submandibular triangle, locate the superficial part of the submandibular gland.
Note: The submandibular gland is one of the three main salivary glands (parotid, submandibular, and sublingual glands), and is innervated by postganglionic branches from the submandibular ganglion. Presynaptic (preganglionic) parasympathetics are derived from the chorda tympani n. (CN VII).The superficial portion of this gland is located in the submandibular triangle near the angle of the mandible.
Photo 10. Suprahyoid mm.
10.) Locate the facial a.
Note: The facial a. traverses the submandibular triangle before emerging over the body of the mandible (anterior to the masseter m.), accompanied by the facial v., deep to the branches of the facial n. The artery ascends and supplies structures of the face.
Photo 11. Facial a. & v.
11.) Identify any submandibular and submental lymph nodes in this area. Recall that lymph nodes are often difficult to distinguish and are easily removed during other dissection procedures, such as skinning or during reflection of muscles.
Note: There are typically three submandibular nodes: one is typically located anterior to the superficial part of the submandibular gland, while the other two are positioned on either side of the facial a. near the ramus of the mandible. Many smaller lymph vessels from a wide area drain into the submandibular lymph nodes (nose, cheek, upper and lateral lip areas).
Note: Submental nodes are located in the submental triangle and drain the structures within the submental triangles on the inferior portion of the mylohyoid mm, and will drain into either the submandibular or jugulo-omohyoid nodes.
Photo 12. Submandibular and submental lymph nodes
12.) Clean the stylohyoid m., and observe the muscle’s attachment sites.
Note: The stylohyoid m. is located medial and parallel to the posterior belly of digastric m. The stylohyoid m. belly divides around the intermediate tendon of the digastric m. Like the posterior belly of the digastric m., the stylohyoid m. is innervated by the facial n. (CN VII). It elevates the hyoid bone.
Photo 13. Stylohyoid m.
13.) Cut the intermediate tendon of the digastric m. Reflect the posterior belly of the digastric m. superolaterally. In addition, relieve the stylohyoid m. from the hyoid bone, and reflect it superiorly. The retromandibular v. may also be reflected superiorly.
Photo 14. Procedural: cutting the intermediate tendon on the digastric m.
14.) Locate the terminal branches of external carotid a.: maxillary a. and superficial temporal a. Recall that the superficial temporal a. was located superior to the parotid gland earlier in this lab.
Photo 15. Terminal branches of the external carotid a.
Note: The maxillary a. is significantly larger than the superficial temporal a., but will be better visualized during dissection of the infratemporal fossa. The maxillary a. extends from the external carotid a. to the pterygopalatine fossa, and has three parts: mandibular, pterygoid, and pterygopalatine.
15.) Locate as many of the branches of the external carotid a. as possible. Specifically locate: superior thyroid a. (and nearby superior thyroid v.), lingual a., and facial a.
Note: The external carotid a. is the primary source of blood to the face and superficial head. The external carotid has eight branches:
- superior thyroid a.,
- ascending pharyngeal a.,
- lingual a.,
- facial a.,
- occipital a.,
- posterior auricular a.,
- maxillary a.,
- superficial temporal a.,
which may be remembered by the mnemonic: “Some Anatomists Like Freaking Out Poor Medical Students.”
Note: The superior thyroid a. is typically the first anterior branch of the external carotid a., and descends to the thyroid gland. The superior laryngeal a. is a branch of the superior thyroid a., and accompanies the internal br. of superior laryngeal n. through the thyrohyoid membrane.
Photo 16. Superior thyroid a.
Note: The lingual a. and facial a. are anterior branches of the external carotid a, and are typically the largest of the proximal external carotid branches. The facial a. may branch from the external carotid a. in a common branch with, or just superior to, the lingual a. The lingual a. can be seen in this area passing deep to the hyoglossus m. to supply the majority of the floor of the mouth and tongue. This artery will be further dissected in the oral cavity.
Photo 17. Facial and lingual aa.
16.) Locate the hypoglossal n. (CN XII) in association with the facial a. as it passes deep to the mylohyoid m.
Note: The hypoglossal n. (CN XII) provides efferent innervation to nearly all extrinsic and intrinsic muscles of the tongue, excluding palatoglossus m. (innervated by the vagus n., CN X).
Photo 18. Hypoglossal n. (CN XII), facial a., mylohyoid m.
17.) Deep to the hypoglossal n. (CN XII) and the mylohyoid m., identify the hyoglossus m. The mylohyoid m. and submandibular gland may need to be reflected, for this identification. If needed, relieve the mylohyoid m. from its attachment to the mandible (mylohyoid line), and reflect towards the hyoid. The submandibular gland can be reflected superiorly. Retain all neurovasculature in this area.
Note: The hyoglossus m. extends from the greater horn and body of the hyoid bone to the side of the tongue. When contracted, the hyoglossus depresses the side of the tongue and retracts the tongue.